When abnormalities such as peeling, discoloration, scratching or the like arise in the paint films on automobile bodies or the like they are repaired using repair paint materials. Automobile repairs can be broadly classified as edge to edge repairs and spot repairs. Edge to edge repairs are carried out when the part which is to be repaired is comparatively large and when repairing the center portion of an automobile part, and the whole of the part is painted with the repair paint. On the other hand spot repair is carried out when the part which is to be repaired is small or when the location of the part to be repaired is not in a prominent position.
In general, spot repairs involve sanding the part which is to be repaired, painting the surface as required and drying and then sanding again and applying the top paint. In this partial painting process, gradation painting is carried out with the clear paint so that the appearance of the unrepaired part does not show a discontinuity from the part which is the subject of the repair. Gradation painting with the clear paint is a process in which clear paint which has been over-diluted with thinner, a liquid mixture of gradation agent and clear paint, or just the gradation agent itself, is applied in the mist part in such a way that there is a gradient of paint film thickness from the repair part to the unrepaired part and in such a way that little mist is deposited on the surrounding part. After drying, the surrounding mist produced by the gradation painting with the clear paint is polished off by polishing. If the polishing in this polishing process is inadequate then the mist is not completely removed and if the polishing is too severe when removing the mist then the clear paint peels away at the boundary line and there is a problem in that a trace of the repair remains. Thus, the gradation painting and polishing processes are processes which require the person completing the repair to be highly skilled.
On the other hand, in many cases a scratch-resistant clear paint which is not prone to scratching by the rubbing forces which are imposed by car washing brushes and the like is applied for the top coat paint film which is coated on an automobile body or the like. Scratch-resistant paint films are either of the type where the paint film is harder than a conventional clear paint film and not liable to scratching or of the re-flow type which is temporarily deformed by the rubbing force of a brush or the like and then immediately reverts to its original form. With both types of scratch-resistant clear paint film the process of polishing off the mist in the spot repair of the repair clear paint film is difficult because of the non-scratch nature, and there is a problem in that a polishing process of long duration is required to polish off the mist. Furthermore, peeling of the clear paint film at the repair boundary line due to the excessive polishing occurs with such scratch-resistant clear paint films, the boundary line between the repair part and the unrepaired part is revealed and there is a problem in that a continuous appearance is not obtained.
In order to deal with these problems there is disclosed in Japanese unexamined patent application laid open H7-118605, for example, a technique in which both scratch resistance and polishability are provided by using a specified paint composition for the top coat. However, although the scratch resistance and the polishability of the part which is the subject of the repair are improved with this technique, there is a weakness in that the polishability of the mist part outside the repaired part is unsatisfactory.
On the other hand, in recent years there has been a strong demand for the establishment of a method of repair which provides a continuous appearance where the boundary line between the repaired part and the unrepaired part cannot be distinguished when the scratch-resistant clear paint film on an automobile body or the like has been partially repaired.
Furthermore, a method in which a thinner for repair purposes which contains surfactant is applied has been disclosed as a method for the spot repair of paint films which enables the repair to carried out easily in such a way that the appearances of the repair part and the dust part surrounding the repair part are of the same the repair paint film (for example, see Japanese unexamined patent application laid open 2001-58156). However, with this method there is a weakness in that the appearance of the repair part and the unrepaired part is discontinuous when a scratch-resistant clear paint is repaired.
Furthermore, a grading liquid composition which contains (1) (A) acrylic resin which includes hydroxyethyl (meth)acrylate and an adduct of hydroxyethyl (meth)acrylate and ε-caprolactone and (B) resin which contains polycaprolactone polyol, (2) organic solvent which includes from 30 to 100 mass % of polar solvent of boiling point from 120 to 230° C., in proportions (by mass) of (1)/(2) of from 1/99 to 5/95, and (3) dibutyltin dilaurate in an amount of from 0.03 to 0.05 parts by mass per 100 parts by mass of the solid fraction of the grading liquid composition has been disclosed as a grading liquid composition which can provide excellent scratch resistance and coated film cut resistance in the repair part and the part surrounding the repair part of an automobile outer paint film (for example, see Japanese unexamined patent application laid open 2007-169526). However, in this case there is a weakness in that the smoothness of the paint film is lost with the use of the ε-caprolactone adduct which is of high polarity.
The present invention is intended to provide a method for the spot repair of scratch-resistant paint films which are scratch-resistant clear paint films on an automobile body or the like, with which mist outside the part which is the subject of the repair is polished off easily and with which peeling of the thin film part of the clear paint film is not liable to occur, and with which it is possible to obtain an appearance where it is difficult to find the boundary line between the repaired part and the unrepaired part.
The present inventors have discovered as a result of thorough research carried out with a view to realizing the aforementioned aim that the intended aims can be achieved by means of a method of repair which includes specified processes, and the present invention is based upon this discovery.